Settable composition containing potassium chloride

ABSTRACT

The present invention relates to settable compositions for general purpose concrete construction containing Class-F fly ash, Class-C fly ash and/or slag, and potassium chloride (KCl) as a substantial replacement for Portland cement conventionally used in such compositions. The potassium chloride is an additive for improved high early strength and accelerated setting times, thereby allowing the concrete structure to be put into service sooner, reducing labor cost, and allowing precast concrete and concrete masonry manufacturers to achieve rapid form and mold turnover.

[0001] This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 09/982,854, filed Oct. 22, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of settablecompositions for general purpose concrete mixes, and more particularlyto settable compositions containing additives for improved strength andshortened setting times.

BACKGROUND OF THE INVENTION

[0003] The present invention is concerned with the utilization ofpotassium chloride (KCI) as an additive for improving the one-daystrength and for shortening the setting times of concrete mixes.Further, the invention is also concerned with the utilization of threeindustrial by-products; namely, Class-F fly ash, Class-C fly ash, andblast furnace slag in general purpose concrete-making compositions.

[0004] When finely divided or pulverized coal is combusted at hightemperatures, for example, in boilers for the steam generation ofelectricity, the ash, consisting of the incombustible residue plus asmall amount of residual combustible matter, is made up of twofractions, a bottom ash recovered from the furnace or boiler in the formof a slag-like material and a fly ash which remains suspended in theflue gases from the combustion until separated therefrom by knownseparation techniques, such as electrostatic precipitation. This fly ashis an extremely finely divided material generally in the form ofspherical bead-like particles, with at least 70 percent by weightpassing a 200 mesh sieve, and has a generally glassy state resultingfrom fusion or sintering during combustion. As recognized in theAmerican Society of Testing Materials (ASTM) specification designationsC618-00 entitled “Fly Ash and Raw or Calcined Natural Pozzolan for Useas a Mineral Admixture in Portland Cement Concrete” and D5370-96entitled “Standard Specification for Pozzolanic Blended Materials inConstruction Application,” fly ash is subdivided into two distinctclassifications; namely, Class-F and Class-C. The definitions of thesetwo classes given in the aforementioned ASTM specifications are asfollows:

[0005] “Class-F—Fly ash normally produced from burning anthracite orbituminous coal that meets the applicable requirements for this class asgiven herein. This class fly ash has pozzolanic properties.

[0006] Class-C—Fly ash normally produced from lignite or subbituminouscoal that meets the applicable requirements for this class as givenherein. This class of fly ash, in addition to having pozzolanicproperties, also has some cementitious properties. Some Class-C flyashes may contain lime contents higher than 10 percent.”

[0007] The latter reference to “pozzolanic properties” refers to thecapability of certain mixtures that are not in themselves cementitious,but are capable of undergoing a cementitious reaction when mixed withcalcium hydroxide in the presence of water. Class-C fly ash possessesdirect cementitious properties as well as pozzolanic properties. ASTMC618-00 is also applicable to natural pozzolanic materials that areseparately classified as Class N but are not pertinent here.

[0008] As the above quotation from the ASTM specification indicates, thetype of coal combusted generally determines which class fly ash results,and the type of coal in turn is often dependent upon its geographicorigin. Thus, Class-C fly ash frequently results from the combustion ofcoals mined in the Midwest United States; whereas Class-F fly ash oftencomes from combustion of coals mined in the Appalachian region of theUnited States. The ASTM specification imposes certain chemical andphysical requirements upon the respective fly ash classifications whichare set forth in U.S. Pat. No. 5,520,730, the disclosure of which isincorporated herein by reference.

[0009] Blast furnace slag is a by-product of the production of iron in ablast furnace; silicon, calcium, aluminum, magnesium and oxygen are themajor elemental components of slag. Blast furnace slags includeair-cooled slag resulting from solidification of molten blast furnaceslag under atmospheric conditions; granulated blast furnace slag, aglassy granular material formed when molten blast furnace slag israpidly chilled as by immersion in water; and pelletized blast furnaceslag produced by passing molten slag over a vibrating feed plate whereit is expanded and cooled by water sprays, whence it passes onto arotating drum from which it is dispatched into the air where it rapidlysolidifies to spherical pellets. In general the glass content of theslag determines the cementitious character. Rapidly cooled slags have ahigher glass content and are cementitious; slowly cooled slags arenon-glassy and crystalline and, thus do not have significantcementitious properties.

[0010] The quantities of these by-product materials that are producedannually are enormous and are likely only to increase in the future. Aspetroleum oil as the fuel for the generation of electricity is reducedbecause of conservation efforts and unfavorable economics, and aspolitical considerations increasingly preclude the construction of newnuclear power electrical generating facilities, or even the operation orcontinued operation of already completed units of this type, greaterreliance will necessarily fall on coal as the fuel for generatingelectricity. As of 1979, the volume of Class-F fly ash that wasavailable then was estimated to be about five times what could bereadily utilized. The estimated annual total production of coal ash inthe U.S. is about 66.8 million tons, while the annual total coal ashsales in the U.S. is only about 14.5 million tons. Further, in Canada,the recovery of copper, nickel, lead and zinc from their ores producesover twelve million tons of slag per year, which is usually accumulatednear the smelters with no significant use. Obviously, there is an urgentand growing need to find effective ways of employing these unavoidableindustrial by-products since they will otherwise collect at a staggeringrate and create crucial concerns regarding their adverse environmentaleffects.

[0011] Various proposals have already been made for utilizing both typesof fly ash. According to Lea (1971), The Chemistry of Cement andConcrete, Chemical Publishing Company, Inc., page 421 et seq., fly ash,i.e., Class-F type, from boilers was first reported to be potentiallyuseful as a partial replacement for Portland cement in concreteconstruction about 50 years ago, and its utilization for that purposehas since become increasingly widespread. It is generally accepted thatthe proportion of Portland cement replaced by the usual fly ash shouldnot exceed about 20 percent to avoid significant reduction in thecompressive strength of the resultant concrete, although some morecautious jurisdictions may impose lower limits, e.g., the 15 percentmaximum authorized by the Virginia Department of Highways andTransportation (VDHT). As described in Lea on page 437, the substitutionof fly ash tends to retard the early rate of hardening of the concreteso that the concrete exhibits up to a 30 percent lower strength afterseven days testing and up to a 25 percent lower strength after 28 daysof testing, but in time the strength levels normalize at replacementlevels up to 20 percent. Increasing the substitution quantity up to 30percent gives more drastic reduction in the early compression values aswell as an ultimate strength reduction of at least about 15 percentafter one year.

[0012] The limited substitution of fly ash for Portland cement inconcrete formulations has other effects beyond compressive strengthchanges, both positive and negative. The fly ash tends to increase theworkability of the cement mix and is recognized as desirably reducingthe reactivity of the Portland cement with so-called reactiveaggregates. On the other hand, fly ash contains a minor content ofuncombusted carbon that acts to absorb air entrained in the concrete.Because entrained air desirably increases the resistance of the hardenedconcrete to freezing, such reduction in entrained air is undesirable,but can be compensated for by the inclusion as an additive of so-calledair-entraining agents.

[0013] Dodson, et al. in U.S. Pat. No. 4,210,457, while recognizing theaccepted limit of 20 percent replacement with fly ash of the Portlandcement in concrete mixes, proposes the substitution of larger amounts,preferably 50 percent or more, of the Portland cement with particularselected fly ashes having a combined content of silica, alumina andferric oxide content, less than 80 percent by weight, and a calciumoxide content exceeding 10 percent, based on five samples of such ashes,varying from about 58-72 percent combined with a calcium oxide range ofabout 18-30 percent. Six other fly ash samples that are not suitable atthe high replacement levels of 50 percent or more were shown to vary inthe combined oxide content from about 87-92 percent and in calcium oxidecontent from about 4 percent to about 8 percent. Evaluating these valuesagainst the ASTM C618-00, one observes that the acceptable fly ashescome under the Class-C specifications, while the unacceptable ashes fellwithin the Class-F specification. Thus, Dodson, et al. in effectestablish that Class-C fly ashes are suitable for substantially higherlevels of replacement for Portland cement in concrete mixes than areClass-F fly ashes, and this capacity is now generally recognized, withClass-C fly ashes being generally permitted up to about a 50 percentreplacement level while maintaining the desirable physical properties ofthe concrete, especially compressive strength.

[0014] In U.S. Pat. No. 4,240,952, Hulbert, et al. while alsoacknowledging the generally recognized permissible limit of Class-F flyash replacement for Portland cement of 20 percent, propose replacementof at least 50 percent and up to 80 percent, provided the mix containsas special additives about 2 percent of gypsum and about 3 percent ofcalcium chloride by weight of the fly ash. The fly ash described forthis purpose, however, was a Class-C fly ash analyzing about 28 percentcalcium oxide and combined silica, alumina and ferric oxide content ofabout 63 percent. With up to 80 percent of this fly ash and thespecified additives, compressive strengths comparable to straightPortland cement were said to be generally achievable. In one exampleusing 140 pounds Portland cement and 560 pounds of fly ash (20:80 ratio)with conventional amounts of coarse and fine aggregate, and water andincluding the requisite additives, compressive strengths tested at 3180psi for 7 days, 4200 psi for 14 days and about 5000 psi at 28 days.

[0015] In U.S. Pat. Nos. 4,018,617 and 4,101,332, Nicholson proposed theuse of mixtures of fly ash (apparently Class-F in type), cement kilndust and aggregate for creating a stabilized base supporting surfacereplacing conventional gravel or asphalt aggregate stabilized bases inroad construction wherein the useful ranges were fly ash 6-24 percent,CKD (cement kiln dust) 4-16 percent and aggregate 60-90 percent, with 8percent CKD, 12 percent fly ash and 80 percent aggregate preferred.Compressive strength values for such measures as revealed in theexamples varied rather erratically and generally exhibited only smallincreases in compressive strength over the 7 to 28 day test period.Among the better results were for the preferred mixture wherein thevalues increased from about 1100 psi at 7 days to 1400 psi at 28 days.The addition of a small amount of calcium chloride improved those valuesby about 200 psi. On the other hand, the addition of 3 percent of limestack dust recovered from a lime kiln significantly reduced the resultsto about 700 psi at 7 days to 900-1300 psi at 28 days. Elimination ofthe aggregate reduced the strength to a fraction of the values otherwiseobtained, a mixture of 12 percent CKD and 88 percent fly ash aloneshowing strength values of only about 190-260 psi over the 28-day testperiod. Similarly, the choice of a finely divided aggregate such as fillsand resulted in about the same fractional level of strength values inthe range of about 140-230 psi. A combination of finely divided andcoarse aggregate in approximately equal amounts reduced the compressivestrength values by about 50 percent with virtually no change over thetest period, giving values ranging from 650-750 psi, except where 1percent of Type 1 Portland cement was included which restored thestrength values to about their original level, except at the initial 7days period where the strength values were about 800-900 psi, increasingat 28 days to about 1200-1600 psi. Curiously, the best strength resultswere attained when 11.6 percent fly ash was combined with 3.4 percentlime with the balance crushed aggregate, the CKD being omitted entirely,for which the strength values while starting at a lower level of about850-950 at 7 days increased to about 1700 psi at 28 days.

[0016] The combination of fly ash and lime stack dust incidentallymentioned in the later patent was explored further by Nicholson in U.S.Pat. No. 4,038,095 which concerns mixtures of about 10-14 percent flyash, about 5-15 percent lime stack dust with the balance aggregate inthe range of 71-85 percent. Somewhat inexplicably, the compressiveresults reported here for such mixtures do not reach the high levelspecified in the first two aforementioned Nicholson patents, thestrength values specified being only about 1000 psi with the moregeneral levels well below that depending on particular proportions.

[0017] In U.S. Pat. No. 4,268,316, Wills, Jr. discloses the use ofmixtures of kiln dust and fly ash as a replacement for ground limestoneand gypsum for forming a mortar or masonry cement, using proportions ofabout 25-55 percent Portland cement, about 25-65 percent CKD and 10-25percent fly ash. When these mortar formulations were mixed with dampsand in the proportions of about one part cement mixture to 2.5-3 partssand, compression strengths comparable to those of standard masonrycement composed of 55 percent cement clinkers, 40 percent limestone and5 percent gypsum were shown for mixtures containing 50 percent cement,24-40 percent CKD and 15-25 percent fly ash. Inexplicably, in oneexample, when the cement content was increased to 55 percent with 35percent CKD and 10 percent fly ash, the compressive strengths dropped byabout 30-40 percent at both the 7 day and 28 day ages to levels inferiorto the standard material. As the cement content was decreased, withcorresponding increases in the CKD, the compressive strength valuesdropped drastically. On the other hand, in another similar example,mixtures containing 55 percent cement, 35 percent CKD and 10 percent flyash proved superior in compressive strength, particularly at the 28 dayage, to mixtures containing 50 percent cement, 35 percent fly ash and 15percent CKD, as well as other standard masonry cements containing 50percent cement, 47 percent limestone and 3 percent gypsum. Indeed,strength values dropped about 40 percent for the mixtures having a 5percent reduction in cement and a corresponding 5 percent increase inthe fly ash to values definitely inferior to the standard cements.Similar variations were shown under laboratory test conditions forcomparable 50/35/15 mixtures dependent on the source of the fly ashwhile under actual construction conditions for the same mixtures,compressive strength values were reduced by about 50 percent for boththe conventional masonry cement containing 55 percent Portland cementand comparable mixtures within the patented concept. The fly ash herewas preferably Class-F with Class-C materials being less desirable.

[0018] In U.S. Pat. No. 4,407,677, Wills, Jr. went on to teach that inthe manufacture of concrete products such as blocks or bricks, the flyash usually employed in combination with Portland cement therein couldbe replaced in its entirety by CKD with modest improvement in earlycompressive strength values for such products. Thus, at one-day andtwo-day tests compressive strength values of about 500-800 psi wereshown, but were said to increase to about 1200 psi after 28 days. Themixes disclosed in Wills, Jr. '677 contained 0.4-0.9 parts cement, about0.1-0.6 parts CKD and 10-12 parts aggregate combining both fine andcoarse materials, such as expanded shale and natural sand in a weightratio of 80/20. Masonry cements generally develop at least about 95percent of their strength properties at 28 days age so that additionalaging of the patented products would not be expected to result in anysignificant increase in their compressive strength values.

[0019] U.S. Pat. Nos. 5,520,730 and 5,266,111 of the present inventor,disclose a general purpose concrete composition comprising Portlandcement, Class-F fly ash, and CKD. The patents also disclose a “syntheticClass-C fly ash blend” comprising Class-F fly ash and CKD. These patentsdisclose the advantages of early strength of concrete; however,utilization of potassium chloride as a cement additive is not disclosed.

[0020] In U.S. Pat. No. 5,032,181, Chung discloses a carbon reinforcedcement that displays high tensile and flexural strengths. During thefabrication of the cement, an accelerating agent mixture is also added.The accelerating mixture comprises polyethanolamine plus either (1)metal sulfate and metal aluminum sulfate, or (2) metal nitrite and metalchloride. The metal sulfate can be potassium sulfate; and the metalchloride can be potassium chloride. There is no disclosure in the patentregarding the one-day strength of the disclosed general purpose concretecompositions.

[0021] None of the above patents addresses the issue of early strengthand setting times of concrete; therefore, there remains a need forconcrete mixes with high early strength and fast setting times, becausethe addition of fly ash to concrete often results in slow setting. Thereare many advantages for having high early strength and fast settingtimes, such as allowing the concrete structure to be put into servicesooner, thereby reducing labor cost, and allowing precast concrete andconcrete masonry manufacturers to achieve rapid form and mold turnover.

SUMMARY OF THE INVENTION

[0022] An advantage of the present invention is to provide a settablecomposition for improved early strength comprising cement and potassiumchloride. In a preferred embodiment, the cement is present in an amountgreater than about 50 percent by weight, the potassium chloride ispresent in an amount of about 1 percent to about 5 percent by weight.

[0023] A further advantage of the present invention is to provide asettable composition for improved early strength comprising cement,Class-F fly ash, and potassium chloride. In a preferred embodiment, thecement is present in an amount greater than about 50 percent by weight,the Class-F fly ash is present in an amount of about 20 percent to about30 percent by weight, and the potassium chloride is present in an amountof about 1 percent to about 5 percent by weight.

[0024] A further advantage of the present invention is to provide asettable composition for improved early strength comprising cement,Class-C fly ash, and potassium chloride. In a preferred embodiment, thecement is present in an amount greater than about 50 percent by weight,the Class-C fly ash is present in an amount of about 20 percent to about30 percent by weight, and the potassium chloride is present in an amountof about 1 percent to about 5 percent by weight.

[0025] A further advantage of the present invention is to provide asettable composition for improved early strength comprising cement,Class-C fly ash, Class-F fly ash, and potassium chloride. In a preferredembodiment, the cement is present in an amount greater than about 50percent by weight, the Class-C fly ash is present in an amount of about10 percent to about 20 percent by weight, the Class-F fly ash is presentin an amount of about 10 percent to about 20 percent by weight, and thepotassium chloride is present in an amount of about 1 percent to about 5percent by weight.

[0026] A further advantage of the present invention is to provide asettable composition for improved early strength comprising cement,slag, and potassium chloride. In a preferred embodiment, the cement ispresent in an amount greater than about 50 percent by weight, the slagis present in an amount of about 20 percent to about 50 percent byweight, and the potassium chloride is present in an amount of about 1percent to about 5 percent by weight.

[0027] Methods of making concrete from the above compositions are alsodisclosed.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Several different types of Portland cement are available and allare useful with the present invention. Type I is the general purposevariety and is most commonly employed, but Type III can also be used forthe early strength application of the present invention. Commercialblended cements, such as Type I-P, wherein 20 percent Class-F fly ash isblended with 80 percent by weight Portland cement clinker duringpulverization should be avoided.

[0029] Any standard or common Class-F fly ash obtained from boilers andlike furnaces used for the combustion of pulverized coal, particularlyof a bituminous or anthracite type, and especially from coal-fired,steam-generating plants of electrical utilities, is suitable for use asthe Class-F fly ash component of this invention. Such fly ash shouldhave a combined silica, alumina and ferric oxide content of at leastabout 70 percent and preferably 80 percent or higher by weight and alime (CaO) content below about 10 percent, usually about 6 percent byweight or less.

[0030] Any standard or common Class-C fly ash obtained from the burningof lignite or subbituminous coal is suitable for use as the Class-C flyash component of this invention. Such Class-C fly ash generally containsmore calcium and less iron than Class-F fly ash and has a lime contentin the range of 15 percent to 30 percent.

[0031] Likewise, any blast furnace slag is appropriate for the presentinvention. Slag is a non-metallic coproduct produced in the productionof iron in a blast furnace. It consists primarily of silicates,aluminosilicates and calcium-alumina-silicates. The molten slag usuallycomprises about twenty percent by mass of iron production. Differentforms of slag products are produced depending on the method used to coolthe molten slag. These products include air-cooled blast furnace slag,expanded or foamed slag, pelletized slag, and granulated blast furnaceslag. Granulated blast furnace slag satisfying the ASTM 989specification is preferred.

[0032] Any potassium chloride is appropriate for the present invention.Potassium chloride is a ubiquitous salt generally occurring as a whitegranular powder or colorless crystal. Commercially, potassium chlorideis available in a wide range from pharmaceutical grade to potash (about96 percent KCI) for fertilizer. Although any potassium chloride isappropriate for the present invention, cost is a major considerationbecause potassium chloride is available in many grades. Therefore, theleast expensive form of potassium chloride that is effective for thepresent invention is most preferred.

[0033] As will be established hereinafter, within the above limits forthe compositions of the invention, the concretes produced therefromexhibit substantially comparable or superior properties for use ingeneral purpose cement construction, especially one-day compressivestrength to corresponding all Portland cement mixes.

[0034] Concrete mixes using the present invention may also containaggregate materials. The choice of aggregate material for concrete mixesusing the present blends will pose no problem to the person skilled inthe design of such mixes. The coarse aggregate should have a minimumsize of about ⅜ inch and can vary in size from that minimum up to oneinch or larger, preferably in gradations between these limits. Crushedlimestone, gravel and the like are desirable coarse aggregates, and thematerial selected in any case should exhibit a considerable hardness anddurability inasmuch as crumbly, friable aggregates tend to significantlyreduce the strength of the ultimate concrete. The finely dividedaggregate is smaller than ⅜ inch in size and again is preferablygraduated in much finer sizes down to 200-sieve size or so. Groundlimestone, sand and the like are common useful fine aggregates.

[0035] In accordance with the present invention, silica fume can also beadded to the cement mixture to achieve high strength and chlorideprotection for the concrete. Silica fume is preferably used from 3-12percent of the amount of cement that is being used in the mixture.

[0036] Other additives can also be used in accordance with the presentinvention, including, but is not limited to, water reducers,accelerators, air entrainment agents, as well as other additives thatare commonly used in the concrete industry.

[0037] The mixes of the invention are prepared by homogeneously anduniformly mixing all of the mix ingredients including the Class-F flyash, Class-C fly ash, slag, and potassium chloride. Mixing can beaccomplished with mixing techniques commonly employed in the concretemix industry. The ultimate compositions are no more susceptible toundergoing separation during handling and storage than are ordinaryconcrete mixes. They can be transported and stored in the same manner asthe ordinary mixes, as can the individual ingredients. The storagecontainers should, of course, be closed to protect the contents thereoffrom weather.

[0038] The following examples are given to illustrate the presentinvention. It should be understood that the invention is not limited tothe specific conditions or details described in these examples.

[0039] The results in the following examples were actually obtained bypreliminarily blending, in each case, the Class-F fly ash, Class-C flyash, slag, and potassium chloride together and combining the blend withthe other mix ingredients. However, the results would be identical ifthe same proportionate amount for each of the component was addedseparately to the remaining mix ingredients and the proportionateamounts of the Class-F fly ash, Class-C fly ash, slag, and potassiumchloride have been expressed in each case in terms of their relativeweight percentages of the particular mix.

EXAMPLE 1

[0040] TABLE 1A Setting Time Cement KCl (minutes) Mix # (%) (%) 1 DayPSI Initial Final 1 100 0 2670 230 315 2 98.5 1.5 4060 210 285 3 97 34520 195 250 4 95.5 4.5 4260 175 235

[0041] TABLE 1B Mix # 7 Day PSI 28 Day PSI 1 5780 7660 2 6560 7550 36410 7260 4 6160 6780

[0042] In Example 1, the cements which include potassium chloride (Mix#2-4) are compared with the cement without potassium chloride (Mix #1).Samples were tested for compressive strength in accordance with ASTMC-109 and for setting times in accordance with ASTM C-403/C-403M-99.

EXAMPLE 2

[0043] TABLE 2A Setting Time Cement Class-F fly KCl (minutes) Mix # (%)ash (%) (%) 1 Day PSI Initial Final 5 70 30 0 1860 290 390 6 70 28.5 1.52840 225 305 7 70 27 3 3090 215 300 8 70 25.5 4.5 2960 200 275

[0044] TABLE 2B Mix # 7 Day PSI 28 Day PSI 5 4310 6030 6 4990 6000 74910 5890 8 4710 5740

[0045] In Example 2, the cements which include Class-F fly ash andpotassium chloride (Mix #6-8) are compared with the cement with Class-Ffly ash only (Mix #5). Samples were tested for compressive strength inaccordance with ASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

EXAMPLE 3

[0046] TABLE 3A Setting Time Cement Class-C fly KCl (minutes) Mix # (%)ash (%) (%) 1 Day PSI Initial Final  9 70 30 0 2080 380 460 10 70 28.51.5 3020 305 375 11 70 27 3 3500 280 340 12 70 25.5 4.5 3320 255 305

[0047] TABLE 3B Mix # 7 Day PSI 28 Day PSI  9 6000 7820 10 5780 7030 115630 6700 12 5480 6380

[0048] In Example 3, the cements which include Class-C fly ash andpotassium chloride (Mix #10-12) are compared with the cement withClass-C fly ash only(Mix #9). Samples were tested for compressivestrength in accordance with ASTM C-109 and for setting times inaccordance with ASTM C-403/C-403M-99.

EXAMPLE 4

[0049] TABLE 4A Setting Time Cement Class CF KCl (minutes) Mix # (%) flyash (%) (%) 1 Day PSI Initial Final 13 70 30 0 1960 320 405 14 70 98.51.5 2980 260 335 15 70 97 3 3200 235 300 16 70 95.5 4.5 3190 220 290

[0050] TABLE 4B Mix # 7 Day PSI 28 Day PSI 13 5160 6740 14 5410 6430 155410 6190 16 5050 6020

[0051] In Example 4, the cements which include Class CF fly ash andpotassium chloride (Mix #14-16) are compared with the cement with ClassCF fly ash only (Mix #13). Samples were tested for compressive strengthin accordance with ASTM C-109 and for setting times in accordance withASTM C-403/C-403M-99.

[0052] Class CF fly ash is the product of a mixture of western andeastern coal. An all-western coal produces Class-C fly ash; and anall-eastern coal produces Class-F fly ash. Because of emissions andenvironmental concerns, power plants may burn a mixture of eastern andwestern coals. Further, the percentages of eastern and western coals mayvary according to the needs of the individual power plant. The CF ashused in Example 4 is the product of a 50/50 blend of eastern and westerncoal.

EXAMPLE 5

[0053] TABLE 5A Setting Time Cement Slag KCl (minutes) Mix # (%) (%) (%)1 Day PSI Initial Final 17 70 30 0 2080 245 335 18 70 28.5 1.5 2780 215285 19 70 17 3 3080 195 255 20 70 25.5 4.5 2930 190 240 21 50 50 0 1410275 365 22 49.25 49.25 1.5 1830 230 310 23 48.5 48.5 3 1830 230 310

[0054] TABLE 5B Mix # 7 Day PSI 28 Day PSI 17 4910 6750 18 6040 7610 196240 6990 20 5660 6970 21 4120 6500 22 5020 6810 23 5000 6990

[0055] In Example 5, the cements which include slag and potassiumchloride (Mix #18-20 and 22-23) are compared with cement with slag only(Mix #17 and 21). Samples were tested for compressive strength inaccordance with ASTM C-109 and for setting times in accordance with ASTMC-403/C-403M-99.

[0056] The above examples clearly show improved one day strength andsetting times of concrete by the addition of up to about 5 percentpotassium chloride. The improvement is effective not only for cement,but also for mixes comprising industrial by-products such Class-F flyash, Class-C fly ash, blast furnace slag, and combinations thereof. Theinvention, however, is not limited to the conditions illustrated in theexamples.

[0057] Although certain presently preferred embodiments of the inventionhave been specifically described herein, it will be apparent to thoseskilled in the art to which the invention pertains that variations andmodifications of the various embodiments shown and described herein maybe made without departing from the spirit and scope of the invention.Accordingly, it is intended that the invention be limited only to theextent required by the appended claims and the applicable rules of law.

What is claimed is:
 1. A settable composition comprising cement, slag,and potassium chloride.
 2. The composition of claim 1, wherein thecement is Portland cement.
 3. The composition of claim 1, wherein thecement is present in an amount of at least about 50 percent by weightbased on the total weight of the settable composition.
 4. Thecomposition of claim 1, wherein the slag is present in an amount ofabout 5 percent to about 50 percent by weight based on the total weightof the settable composition.
 5. The composition of claim 1, wherein thepotassium chloride is present in an amount of about 1 percent to about 5percent by weight based on the total weight of the settable composition.6. The composition of claim 1, wherein the cement is present in anamount of at least about 50 percent, the slag is present in an amount ofabout 20 percent to about 30 percent, and the potassium chloride ispresent in an amount of about 1 percent to about 5 percent, wherein allpercentages are based on the total weight of the settable composition.7. A method of making concrete comprising steps of i) mixing thesettable composition of claim 1 with water, sand, and gravel to form amixture; ii) forming the mixture into a desired shape; iii) allowing themixture to harden to form concrete.
 8. The method of claim 7, whereinthe cement is Portland cement.
 9. The method of claim 7, wherein thecement is present in an amount of at least about 50 percent by weightbased on the total weight of the settable composition.
 10. The method ofclaim 7, wherein the slag is present in an amount of about 5 percent toabout 50 percent by weight based on the total weight of the settablecomposition.
 11. The method of claim 7, wherein the potassium chlorideis present in an amount of about 1 percent to about 5 percent by weightbased on the total weight of the settable composition.
 12. The method ofclaim 7, wherein the cement is present in an amount of at least about 50percent, the slag is present in an amount of about 20 percent to about30 percent, and the potassium chloride is present in an amount of about1 percent to about 5 percent, wherein all percentages are based on thetotal weight of the settable composition.
 13. The method of claim 7,wherein the forming step comprises pouring the mixture into a form priorto allowing the mixture to harden.